NWEN 241 Assignment 4

NWEN 241 Assignment 4
Weeks 9-11

In this assignment, you will be asked to implement a simple database table using C++
programming constructs.
You must submit the required files to the Assessment System
(https://apps.ecs.vuw.ac.nz/submit/NWEN241/Assignment_4) on or before
the submission deadline. Any assignment submitted up to 24 hours after the deadline
will be penalised by 20%, and any assignment submitted between 24 and 48 hours after
the deadline will be penalised by 40%. Any assignment submitted 48 hours or more after
the deadline will not be marked and will get 0 marks.
Full marks is 100. The following table shows the overall marks distribution:
Criteria Marks Expectations for Full Marks
Compilation 10 Compiles without warnings
Comments 10 Sufficient and appropriate comments
Coding Style 10 Consistent coding style
Correctness 70 Handles all test cases correctly (see
marks distribution below)
Total 100
For the Correctness criteria, the following table shows the marks distribution over the
different task types:
Task Type Marks
Core 45
Completion 15
Challenge 10
Total 70
1
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Introduction
This assignment will test your application of the conceptual knowledge of C++
fundamentals to solve practical programming tasks. You may only use the Standard
C++ Library to perform the tasks in this part.
Sample codes showing examples on how you can test your implementation are
provided under the files directory in the archive that contains this handout file.
Commenting
You should provide appropriate comments to make your source code readable. If your
code does not work and there are no comments, you may lose a major component of
marks for this assignment.
Coding Style
You should follow a consistent coding style when writing your source code. Coding style
(aka coding standard) refers to the use of appropriate indentation, proper placement of
braces, proper formatting of control constructs, and many others. Following a particular
coding style consistently will make your source code more readable.
There are many coding standards available (search "C++ coding style" in Google). The
Google C++ Style guide (which you can access via the link https://google.github.
io/styleguide/cppguide.html) is a good guide to use. Note that you do not have
to follow every recommendation you can find in a coding style document, you just have
to apply that style consistently.
2
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Program Specifications
(This is already partly discussed in Assignment #2.)
A fundamental concept in DBMS is the table. A table consists of zero or more records or
entries, and each record can have one or more fields or columns. An example of a table
that stores information about movies is shown below:
id title year director
10 The Goonies 1985 Richard Donner
23 The Godfather 1972 Francis Ford Coppola
37 Avatar 2009 James Cameron
43 Citizen Kane 1941 Orson Welles
14 The Fellowship of the Ring 2001 Peter Jackson
This table contains 5 records. Each record has 4 fields, namely, id, title, year, and
director.
In this assignment, you will focus on implementing a single database table with 4
fields (id, title, year, and director).
A structure with tag movie will be used for holding a table record. The structure
declaration is given below and is defined within nwen namespace in abstractdb.hpp:
namespace nwen {
struct movie {
unsigned long id;
char title[50];
unsigned short year;
char director[50];
};
}
3
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Task 1.
Core [15 Marks]
Declare a C++ abstract class for representing a database table. The class should be named
AbstractDbTable and should have the following public members:
• A pure virtual function named rows() which returns an integer and does not
modify any member variables.
• A pure virtual function named get() which accepts an integer parameter, returns
a pointer to a movie, and does not modify any member variables.
• A pure virtual function named add() which accepts a movie structure.
• A pure virtual function named update() which accepts an unsigned long integer
and a (non-pointer) movie structure parameters and returns a boolean.
• A pure virtual function named remove() which accepts an unsigned long integer
parameter and returns a boolean.
• A function named loadCSV which accepts a C++ string parameter and returns a
boolean.
• A function named saveCSV which accepts a C++ string parameter and returns a
boolean.
Note that the last two member functions are not pure virtual.
The abstract class should be defined within nwen namespace. Save the class declaration
in a header file named abstractdb.hpp.
4
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Task 2.
Core [10 Marks]
Declare C++ class named VectorDbTable that extends AbstractDbTable. The class
should be concrete, which means that it should provide declarations of all pure virtual
members of AbstractDbTable. Do not include declarations for the member functions
loadCSV() and saveCSV().
You must use a vector as table for storing the movie records. You may declare a default
constructor, additional member variables and functions. Provide sufficient comments to
justify the declaration of these additional members.
The class VectorDbTable should be declared within nwen namespace. Save the class
declaration in a header file named vectordb.hpp.
Task 3.
Core [20 Marks]
Provide implementations for the following member functions of VectorDbTable (which
are inhereted from AbstractDbTable):
• rows(): returns the number of rows in the table.
• get(): returns a pointer to a movie structure. The input parameter indicates the
row number of the record to be returned.
• add(): inserts a record into the table. The input parameter contains the record
details to be stored in the table. If there an existing record in the table with the same
id, then the insertion should not proceed. The function should return true if the
record was successfully inserted into the table, otherwise, it should return false.
• update(): updates a record in the table. The unsigned long integer input
parameter indicates the id of the record to be updated and the structure is the data
the row should be updated with. The function should return true if the update
was successful, otherwise, it should return false.
• remove(): removes a record from the table. The input parameter contains the id
of the record to be removed. The function should return true if the removal was
successful, otherwise, it should return false.
Save the implementation of the above member functions in a C++ source file named
vectordb.cpp.
5
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Task 4.
Completion [15 Marks]
Provide an implementation for the member function saveCSV(). Note that saveCSV()
is declared in AbstractDbTable, hence, you will save your implementation in a C++
source file named abstractdb.cpp.
As mentioned in Task 1, loadCSV() accepts a C++ string parameter which denotes the
filename to which to save the contents of the table.
The function saveCSV() should perform the following:
1. Open the file for writing using C++ File I/O. You are not allowed to use any of the
C File I/O functions. The file must be emptied.
2. Write every record from the table into the file. A record must be written as a commaseparated value (one record per line). For instance, for a movie record with id 37,
title Avatar, year 2009, and director James Cameron, the output should be
37,"Avatar",2009,"James Cameron"
3. Close the file.
The function should return false if:
1. The file cannot be opened for writing.
2. Errors were encountered while writing to the file.
Otherwise, it should return true.
Save the implementation of this function in abstractdb.cpp.
6
NWEN 241 2021-T1 Weeks 9-11 Assignment 4
Task 5.
Challenge [10 Marks]
Provide an implementation for the member function loadCSV(). Note that loadCSV()
is declared in AbstractDbTable, hence, you will save your implementation in a C++
source file named abstractdb.cpp.
As mentioned in Task 1, loadCSV() accepts a C++ string parameter which denotes the
name of a comma-separated value (CSV) file to be loaded. In a valid CSV file, a line
represents a record. An example of a line in a valid CSV file is shown below:
37,"Avatar",2009,"James Cameron"
which has 4 fields (id, title, year, and director) separated by commas.
The function loadCSV() should perform the following:
1. Open the file infn for reading using C++ File I/O. You are not allowed to use any
of the C File I/O functions.
2. Read in all lines from the file. Add every line (which corresponds to a record) from
the file into the table using the add() function declared in AbstractDbTable.
When a line not following the expected format is encountered, the reading of the
rest of the lines is terminated.
3. Close the file.
The function should return false if:
1. The file does not exist or cannot be opened for reading.
2. The file is not a valid CSV file (at least one of the lines does not follow the expected
format.)
Otherwise, it should return true.
Save the implementation of this function in abstractdb.cpp.
7